1 CSCE 4013: Mobile Systems Programming Nilanjan Banerjee Mobile Systems Programming University of Arkansas Fayetteville, AR

2 Few reasons to go MAD with phones… Smart phones Internet access anywhere Social networking Millions of mobile users Open standards

3 Introduction to Android Open software platform for mobile development A complete stack—OS, middleware, and Applications An open Handset Alliance (OHA) project Powered by the Linux OS Fast application development in Java Open source under the Apache 2 license

4 Architecture for Android.

5 Linux kernel Works as the HAL (Hardware Abstraction Layer) Device drivers Memory management Process management Network stack

6 Libraries C/C++ libraries Interfaces through Java Surface manager --- handles the UI Windows 2D and 3D graphics Media Codecs, SQLlite, Browser engine

7 Android runtime Dalvik VM Dex file Compact and efficient than class files Core Libraries Java 5 Std Edition Collections, I/O --- everything that is in standard Java

8 Application Framework API Interface Activity Manager Manages application lifetime

9 Lets jump into a simple Android application

10 Components of an Android application Activity Intent and IntentReceiver Service ContentProvider AndroidManifest (binds all of these together)

11 Activities Typically corresponds to one UI screen But they can be Faceless A floating window Return a value Typically a complex application will have multiple activites E.g., application Activity 1: log in page Activity 2: displaying a set of Transfer data between activities Usually form a bundle and pass it around (we will talk about in detail)

12 Intents A description of what you want done… something like a verb E.g. Intent of a music player is to PLAY Intents are of two types – Implicit and Explicit Explicit Application states which Java function to use Implicit System decides for you which intent is best for you

13 Intents GMail Contacts Home Blogger Chat Client component makes a request for a specific action “Pick photo” Picasa System picks best component for that action New components can use existing functionality Blogger Photo Gallery

14 Intent Receivers Components that respond to broadcast ‘Intents’ Way to respond to external notification or alarms Apps can invent and broadcast their own intent Using intent filters applications can decide which Intent to respond to

15 Services Faceless components that run in the background E.g., music players, network downloads

16 Content Provider Store and retrieves data and makes it accessible to all applications Resources are specific to your application Your application can define a content provider and publish it. Android stores content provider in the form of a database You can access it in your application Android provides audio, video, images, personal information android.provider.Contacts.Phone.

17 Resources Utilities that an application uses and “reuses” Strings, colors, dimensions, style/theme.

18 Application lifecycle onCreate() onStart() onResume() Activity running onPause() Process is killed Activity starts activity comes to foreground activity comes to background onStop() activity is no longer visible

19 Lets look at code again

20 Developing UIs in Android Drag and Drop UI development Using XML + Java Using Java alone (similar to Swing and AWT).

21 Layouts Layouts are defined in a layout file (e.g., main.xml) A layout is made up of Views and ViewGroups. Every layout file has one root view

22 Loading an XML resource When the application is compiled, each XML layout file is compiled into a View resource. This View resource should be loaded in your application code in Activity.onCreate() public void onCreate(Bundle savedInstance) { super.onCreate(savedInstance); setContentView(R.layout.main); }

23 Views and Widgets View is the basis of all UI elements such as Widgets (buttons, TextView, Menus, etc. etc.). It is superclass of all Widget classes Each View or ViewGroup object supports a bunch of XML attributes (properties) ID How do I create an instance of the Widget object from my Java code? android:id = (local resource) android:id = “android:id/zzz” (android resource) Button myButton = (Button) findViewById(R.id.my_button) <Button android:layout_height=“wrap_content” android:layout_width=“wrap_content” android:text=“My Button” />

24 Views and Widgets Layout parameters layout_width, layout_height, layout_margin, wrap_content : use space equal to the text inside the view uses fill_parent: use as much space as used by the parent view dip: density independent pixels Frame layout Designed to display one item at a time You can have multiple widgets but they will be positioned based on top left of the screen Relative layout Helps greatly when you want to place Views relative to previous views placed in the actvity Lets take an example

25 Other interfaces onLongClick() (View.onLongClickListener) When a user touches or holds an item onFocusChange() (View.onFocusChangeListener) Navigates onto or away from an item. onKey() (View.onKeyListener) User is focussed on an item and presses of releases a key

26 Handling UI events

27 Handling UI events

28 Assignment

29 Next class and todolist Continue on application basics for the Android Form your group Pls take a phone if you have already formed a group Set up eclipse with the android SDK and plugin if you have not done so Set up Windows Phone 7 IDE